Nitride semiconductor device

Abstract

According to the nitride semiconductor device with the active layer made of the multiple quantum well structure of the present invention, the performance of the multiple quantum well structure can be brought out to intensify the luminous output thereof thereby contributing an expanded application of the nitride semiconductor device. In the nitride semiconductor device comprises an n-region having a plurality of nitride semiconductor films, a p-region having a plurality of nitride semiconductor films, and an active layer interposed therebetween, a multi-film layer with two kinds of the nitride semiconductor films is formed in at least one of the n-region or the p-region.

The invention claimed is: 
     
       1. A nitride semiconductor device comprising:
 an n-region layer structure including a first n-region multi-film layer composed by subsequently growing three films including a lower film made of an undoped nitride semiconductor, an inter-film made of a nitride semiconductor doped with an n-type impurity and an upper layer made of an undoped nitride semiconductor, said lower film having a thickness in the range of 500 through 8000 angstroms, and said inter-film having a thickness in the range of 150 through 400 angstroms; 
 a p-region layer structure including a p-region multi-film cladding layer having at least one first nitride semiconductor film and at least one second nitride semiconductor film, said at least one second nitride semiconductor film having a different bandgap than said at least one first nitride semiconductor film, at least one of said at least one first and second nitride semiconductor films being doped with a p-type impurity; and 
 an active layer interposed between said n-region and p-region layer structures, said active layer having a multiple quantum well structure including In a Ga 1-a N (0≦a<1) layers; 
 wherein said n-region layer structure further includes an n-contact layer containing the n-type impurity, 
 wherein said first n-region multi-film layer is interposed between said n-contact layer and said active layer. 
 
     
     
       2. A nitride semiconductor device according to  claim 1 , wherein said at least one first nitride semiconductor film has a different concentration of p-type impurity from that of said at least one second nitride semiconductor film. 
     
     
       3. A nitride semiconductor device according to  claim 1 , wherein said first nitride semiconductor film has a same concentration of the p-type impurity as said at least second nitride semiconductor film. 
     
     
       4. A nitride semiconductor device comprising:
 an n-region layer structure including a first n-region multi-film layer composed by subsequently growing three films including a lower film made of an undoped nitride semiconductor, an inter-film made of a nitride semiconductor doped with an n-type impurity and an upper layer made of an undoped nitride semiconductor, said lower film having a thickness in the range of 500 through 8000 angstroms, and said inter-film having a thickness in the range of 150 through 400 angstroms; 
 a p-region layer structure including a p-region single-layered cladding layer doped with a p-type impurity and made of Al b Ga 1-b N (0≦b≦1); and 
 an active layer interposed between said n-region and said p-region layer structures, said active layer having a multiple quantum well structure including In a Ga 1-a N (0≦a<1) layers; 
 wherein said n-region layer structure further includes an n-contact layer containing the n-type impurity, 
 wherein said first n-region multi-film layer is interposed between said n-contact layer and said active layer. 
 
     
     
       5. The nitride semiconductor device according to  claims 1  or  4 ,
 wherein said lower film has a thickness in the range of 1000 through 5000 angstroms and said upper layer has a thickness in the range of 150 through 1000 angstroms. 
 
     
     
       6. The nitride semiconductor device according to one of  claims 1  and  4 , wherein said n-region layer structure further includes a second n-region multi-film layer having at least one of fifth nitride semiconductor films and at least one of sixth nitride semiconductor films with different composition, said second n-region multi-film layer being interposed between said first n-region multi-film layer and said active layer. 
     
     
       7. The nitride semiconductor device according to  claims 1  or  4 , wherein said n-region layer structure further includes an undoped GaN layer on which said n-contact layer is formed.
 wherein said active layer is not contacting with said first n-region multi-film layer. 
 
     
     
       8. The nitride semiconductor device according to one of  claims 1  and  4 ,
 wherein said first n-region multi-film layer is contacting with said n-contact layer. 
 
     
     
       9. The nitride semiconductor device according to  claims 1  or  4 ,
 wherein said lower film, said inter-film and said upper layer have same compositions. 
 
     
     
       10. The nitride semiconductor device according to  claim 9 ,
 wherein said lower film, said inter-film and said upper layer are made of GaN.